1. Field of Invention
This invention relates generally to golf clubs and, more particularly, to a light-weight handle for improving a club's performance.
2. Background
There is an ongoing desire to improve the performance of golf clubs. A modern golf club typically comprises a head connected to a shaft, and a grip attached over a length of the shaft opposite the head. The grip is typically a relatively thick sleeve of molded rubber having an outer diameter that is substantially larger than the shaft diameter so that the grip fits comfortably and securely in the hands of the golfer. Furthermore, the grip usually has a tapered profile. It tapers from a relatively large diameter at the butt end to a relatively small diameter at the other end where the club shaft emerges from the grip. The tapered profile acts like a conical wedge to prevent the club from leaving the hands of the golfer during the swing due to the centrifugal force.
One important parameter affecting golf club performance is its mass distribution. For a golf club of a given mass, the mass distribution determines how much momentum can be imparted to the ball. The greater the imparted momentum, the farther the ball will travel. The center of gravity of the club is one measure of the mass distribution, and is the point where all of the mass of the object can be considered to be concentrated. The closer the center of gravity is to the head of the club, the more effective the mass of the club is in imparting momentum to the ball.
Another important parameter affecting golf club performance is club weight. Heavier clubs tend to be more difficult to accelerate than lighter clubs. Lower acceleration equates to lower swing velocity. Swing velocity is an important factor in driving a ball: for clubs of similar weight and mass distribution, the greater the swing velocity, the farther the ball will travel. Therefore, lighter clubs are preferable from the perspective of swing velocity.
Efforts to improve a club's performance have been focused generally on reducing shaft weight. To this end, a family of clubs having graphite composite shafts has been developed. The high strength to weight ratio of graphite provides for shafts with the strength of steel, but without the weight.
In addition to lightening the shaft, a more recent advance is the elimination of the grip. Although the molded rubber-grip is a highly standardized component of the modern club, its weight has a detrimental effect on the club's performance. It is a relatively heavy part of the club, representing, for example, about 15% of the total mass of a typical driver or any fairway wood. Furthermore, due to the grip's position at the end of the shaft, its weight has a major detrimental influence on both the total weight of the club and its center of gravity. These detrimental effects are amplified for an over-sized grip which are used commonly by people with arthritis or large hands.
The elimination of the conventional grip in these new clubs with gripless graphite shafts is made possible by the molding flexibility of graphite fibers. That is, the diameter of the shaft toward the end opposite the head increases to approximately the size and shape of a conventional grip. By expanding the end of the shaft this way, a user is able to grasp it directly without the need for a grip.
Although graphite shafts tend to reduce shaft weight and can be molded to eliminate the need for a grip, the torsional stiffness of a graphite-shaft is significantly less than that of a steel shaft. For example, for a right-handed golfer, the lower torsional stiffness of a graphite-shaft allows the club head to rotate clockwise about the shaft axis upon impact with the ball. Consequently, the club face does not meet the ball squarely, but rather "toes out" during impact and transfers momentum to the ball at an angle. This causes the ball to veer to the right of its intended path.
The characteristic inaccuracy associated with graphite shafts can be mitigated by angling the face of the golf club's head in a direction opposite of the shaft's twist. For example, the club face would have a counterclockwise angle for a right-handed club. This angle compensates for the shaft's torsional twist such that, upon impact, the club's momentum transfers substantially squarely to the bal. Such compensation, however, is imprecise. The amount of compensation varies not only according to the user, but also according to the strength of a user's particular swing. Consequently, serious golfers prefer not to rely on such compensation. In general, professional golfers do not use graphite shaft clubs but rather continue to use clubs with steel shafts.
The problems facing graphite-shaft clubs also face the new gripless clubs since such clubs, for practical purposes, are restricted to graphite shafts. It is the flexibility of graphite fiber fabrication that enables a shaft to be molded such that the end opposite the head has a size and shape suitable for a user to grip. Attempting to swage a steel shaft to such a form as taught in U.S. Pat. No. 3,809,403 is difficult, if not impossible, because the reduction in diameter from the shaft's gripping portion to the body of the shaft is too great for conventional swaging. It is unlikely that a steel shaft of the thickness typically used could be swaged, using conventional methods, to the dimensions indicated without crenelating. Thus, to realize the benefits of a gripless club, a new gripless graphite-shaft club must be purchased.
Therefore, a need exists to reduce the weight of the club and lower its center of gravity toward the head independent of the shaft material used. This need applies to both new and existing clubs. The present invention fulfills this need among others.